Observation of the Impact of Smart-1
Christian Veillet - Principal Investigator

The impact
The dust cloud
The flash
Crash location
Looking at the big picture...

The observations were made with the WIRCam wide-field infrared camera (learn more about WIRCam here)
10s exposure time - H2 narrow-band filter at 2122  nanometers with a 32 nanometers bandwidth
Image size: 2' x 2' (or  ~200km x 200km) for all images (but the big picture!)

For all pictures - Credit line: "Canada-France-Hawaii Telescope / 2006"
Copyright © 2006 Canada-France-Hawaii Telescope Corporation

The impact

Credit line: "Canada-France-Hawaii Telescope / 2006"
~15s before impact

Credit line: "Canada-France-Hawaii Telescope / 2006"

Credit line: "Canada-France-Hawaii Telescope / 2006"
~15s after the impact...
Nothing is visible anymore...

Here is an animation showing a sequence of 20 images  covering the impact which is seen only on one image.

Looking at the images before and after the impact: the dust cloud

Click here to get a mosaic of  15 exposures starting with the one at the time of the flash, with each having the same size and scale as the pictures below (makes for a big picture!). For an animation worth the first ten exposures, click here!

This an animation showing the scene of the impact from the exposure just before the impact to ~130s later (~10 images). In order to look at the dust generated by the impact, the scene from before the impact has been substracted from all the images.  Each image is a snapshot over 10s, with a gap of around 5s between exposure.  The expansion of the dust cloud is clearly seen...
No processing to enhance the signal and minimize the background noise has been made on these iamges. You can see the effect of some image processing when comparing with the mosaic or the  animation on the  left...

This is an animation generated as on the left,  but looking back in time for ~150s before the impact (a test to show how "uneventful" the scene was before the impact: it gives more confidence to the untrained eyes that indeed is indeed something happening after the impact!)

Looking at the flash

This contour map of the flash, so bright that it is saturated,  shows that the North (top) and South (bottom) of the flash are not identical.  There is a clear elongation on the South side in the direction of the motion.
The elongations at 45 degrees are due to the diffraction pattern from the secondary mirror supports (the spider).

The units on the axes of  the graph are WIRCam pixels: 0.3" or ~0.5km.

Credit line: "Canada-France-Hawaii Telescope / 2006"

Where did Smart-1 crash?

To look at the location of the crash, we use two sets of data:
- the position of the flash relative to a pair of reference craters visible as bright areas on the CFHT images,
- a map of the Moon as seen from Mauna Kea at the time of the impact (thanks to the Moon Virtual Atlas).

A simple triangulation allows to pinpoint the impact area within a couple of kilometers.

The crash site determined from our observations is actually almost where the last predictions placed it a day before the impact

Looking at the big picture!

In case you wonder what the Moon really looked like through WIRCam, you can watch the animation on the left.

WIRCam has a BIG field (20' x 20', like 2/3rd of the Moon).  WIRCam focal plane is an array of four detector, each of them 10'x10'. As the impact was on the South-East of the Moon, the South-East area of the Moon was placed on the North-West corner of the North-West detector... We ended up with only a tiny fraction of the whole field really used to look at the impact (see all the images above). What you see on the right is more or less the entire North-West detector. You can see the stars moving from one exposure to the next as the telescope tracks the Moon, and disappearing behind the Earthsine lit Moon crescent. The extreme upper right is saturated by the Sun as we start looking at the illuminated part of the Moon.

You see, in the center area, ugly reflections coming from the bright Moon through various optics on the way down to the camera. WIRCam was definitely not designed to have such a big and bright light source close by!

You also see the flash popping up on one of the frames in the upper right area. All the images shown above have been extracted form the large (2K x 2K single detector)  images used for this wide angle animation.

If you want a bigger version of the animation, click here.

Mahalo nui to the Smart-1 team for sharing real-time information on the last days of the mission with the astronomical community.

Smart-1 Mission web site at ESA
Bernard Foing  (ESA SMART-1 project scientist)
Pascale Ehrefnreund Leiden University (ground based campaign coordinator)